Donald Trump’s Twitter flexing might have you think otherwise, but it’s not the size of your nuclear weapon that matters: It’s whether you use it. And although Trump’s giant nuclear button may look frightening, it might actually be the smallest nuclear weapons that pose the most potent threat to the doctrine of mutually assured destruction that underpins modern nuclear peace.
This February, the Trump administration released its Nuclear Posture Review, a document detailing its positions on a medley of nuclear issues. Among those positions is a fervent support for investing in tactical nuclear weapons, warheads that are designed for use on the battlefield and thus carry significantly lower payload than traditional nuclear weapons. The B61 Mod 10, an old US tactical nuke, can be set to a yield as low as 300 tons, 50 times less than the payload of the bomb that destroyed Nagasaki; in the 1950s—the more inventive days of the US military—a tactical nuke was designed that could yield as little as 10 tons and be fired from a Jeep.
The administration’s interest in revamping our aging arsenal of tactical nukes is couched in a sentiment familiar to nuclear wonks: We want what the Russians have. Specifically, American generals fear that in certain circumstances—particularly an armed confrontation with NATO member nations—Moscow might be willing to use its own tactical nukes to end conflict quickly and scare the West into negotiating on its terms. American military officials worry that if the US doesn’t have its own low-yield nukes, Russia could use theirs without fear of American retaliation: Since our the US’ possible nuclear response would be escalation using a much larger warhead, Russians could be confident that the US wouldn’t respond with nukes at all. In short, the power of the US’ nuclear weapons would prevent a proportional response.
But this type of argument downplays the chaotic nature of any potential nuclear exchange. To think that launching a smaller nuclear weapon would be less likely to cause escalation is to underestimate the gravity of using a nuke in the first place. Jeffrey Lewis, a nuclear scholar at the Middlebury Institute of International Studies, writes that this is exactly why low-yield weapons are not more credible than their larger counterparts: “Nuclear weapons are nuclear weapons, and it seems very unlikely to me that a president is going to be confident that he can start a limited nuclear war that doesn’t become a very big one, quickly.” After all, it’s difficult to believe that if Russian early-warning detectors were to pick up a nuclear missile launched by the US, Moscow would wait until it detonated in their homeland to measure the size of the blast before retaliating.
The US already has a better option to deter Russian use of nuclear weapons: its staggering conventional military. Michael Krepon, a nuclear security expert and cofounder of the Stimson Institute, believes that “the way to beat tactical nuclear weapons is with overwhelming conventional firepower.” The US still has the largest conventional military force in the world by a massive margin, and with support from its NATO allies—and any other countries outraged by a potential Russian first use—conventional arms would be more than enough to punish any Russian use of tactical nukes.
Best of all, sticking to conventional weapons keeps the US out of situations where it might be tempted to use a nuclear weapon first. Philip Coyle and James McKeon, two experts at the Center for Arms Control and Non-Proliferation, write that tactical nukes actually undermine deterrence and hurt US national security “by lowering the threshold for the use of nuclear weapons, making the unthinkable more likely.” With a less intense blast than traditional nuclear weapons, many military officials—including General James Cartwright, the former head of the US Nuclear Forces—think of tactical nukes as deployable in battle, which could lead to massive retaliation and bloodshed.
And it’s certainly possible that the US might consider using tactical nukes in an otherwise-conventional situation. During the battle of Khe Sanh—one of the most brutal engagements of the Vietnam War—US soldiers were bombarded in a Marine combat base for 77 days. President Lyndon Johnson and his generals, fearing disaster, seriously considered the deployment of tactical nuclear weapons to end the battle. What’s more, maintaining these weapons opens the extremely real possibility of unintentional use. During the Cuban Missile Crisis, a Russian submarine mistook an American destroyer doing a practice drill for an offensive strike. Only the dissent of a single Soviet naval officer interrupted an order to launch a nuclear-armed torpedo and stopped a chain of escalation that could have annihilated millions around the world.
Even if the prospect of the US using a nuclear weapon is slim, investing more in tactical nukes would only heighten the nuclear anxiety felt across the world. Proliferation of any kind continues to strain relations between nuclear powers—particularly on the Korean peninsula—and tactical nukes are becoming a large part of the problem. Most obviously, increasing spending on nuclear weapons continues a dangerous trajectory of nuclear build-up: The recent Russian violation of the Intermediate-range Nuclear Forces Treaty, a US–Soviet treaty requiring the destruction of all ground-based missiles with ranges of 500 to 5500 kilometers, had experts abuzz about an accelerating nuclear arms race. Increasing spending on tactical nukes only adds fuel to the flame.
Even worse would be to send the weapons across the globe, a move the US is nevertheless considering. Late last year, the South Korean defense minister suggested the US move tactical nukes to the Korean peninsula, a maneuver that would inflame Kim Jong-Un’s nuclear rhetoric and legitimize its grievances against Western aggression. It’s unclear why tactical nuclear weapons would even be encouraging to South Korea as a deterrent: If North Korea sticks to conventional belligerence, South Korea can respond with its own conventional weapons. And if Pyongyang were to escalate to a nuclear weapon, Seoul would likely turn to US ICBMs to retaliate, rather than using tactical nukes.
A further problem, as Zachary Keck of the Nonproliferation Policy Education Center explains, is that deploying tactical nukes to South Korea might also catalyze aggression by creating “juicy targets for North Korea to target in the event of conflict.” With the accuracy of Pyongyang’s conventional missiles higher than ever before, a Northern strike aimed at debilitating tactical nukes in the South could easily be the first step in a meltdown of peninsular relations.
Although the Cold War is long behind us, nuclear weapons are still the bedrock of modern geopolitics. The Trump administration’s move towards low-yield nuclear weapons is worrisome, and calls to distribute the weapons around the world are misguided. Certainly Trump’s desires to comfort our allies are legitimate, but developing or deploying tactical nukes seems liable to bring only a higher chance of war—simply taking a hammer to his smartphone would be a far more effective (and cheaper) way to lower nuclear tensions.